A SAHP system combines the heat pum

A SAHP system combines the heat pump technology and solar
thermal energy application in mutual beneficial ways. This combi-nation, to some extent, improves the COP of the heat pump unit
and reduces the consumption of fossil energy resource. According
to different heat transfer mediums filled in the solar collector,
the SAHP systems can be divided into the direct expanded solar as-sisted heat pump (DX-SAHP) system and the indirect expanded
SAHP system. In the DX-SAHP system, the refrigerant works as
the heat transfer medium. For the indirect expanded SAHP system,
which includes the solar assisted air source heat pump (SA-ASHP)
system and the solar assisted water source heat pump (SA-WSHP)
system, the heat transfer medium is usually water, air or antifreeze
solutions etc